Ring-annelated corannulenes as fullerene receptors. A DFT-D study†
Stacking π⋯π interactions of ring-annelated corannulenes with fullerenes C60 and C70 were studied at the B97-D level. For this purpose three-, four-, and five-membered rings (saturated and unsaturated) were annelated to the five rim bonds of corannulene. Substitution effects with NH, O and S units on each one of the five saturated five-membered rings annelated to the rim of corannulene were also evaluated. In all cases, complexation energies were larger than that for the parent compound, corannulene C20H10; in the best case an increase of almost 90% is found. According to our results, the increase of complexation energy is directly related to the increase of the dispersion contribution, where CH⋯π interactions play a very important role. This kind of interaction has special relevance for compounds with saturated annelated rings, where the spatial disposition favours the interaction between hydrogen atoms of CH2 groups and the π cloud of fullerene. For compounds with unsaturated annelated rings the increase of dispersion is not so pronounced; however, this is fairly offset by the increase of the electrostatic interaction. Finally, stacking interactions between ring-annelated corannulenes and fullerene C70 show complexation energy values quite similar to those obtained with fullerene C60.